1. Field of the Invention
The present invention relates to semiconductor integrated circuits having a plurality of programmable elements and lesser pluralities of programming elements and addressing elements involved in the programming of the programmable elements and also to methods for programming the programmable elements.
2. Description of the Related Art
Programmable elements are used, for example, to identify semiconductor wafers and even chips divided therefrom. The programmable elements are typically fuses (open when blown) or `antifuses` (shorted by applying excessive current to the antifuse).
While very convenient for identification purposes, circuits including antifuses are demanding increasing proportions of the semiconductor device area, which is area taken away from the desired end functions of the circuits. Typically, each antifuse is selected in accordance with an address signal and a program signal that are respectively applied to the gates of an MOS transistor pair associated with each antifuse. A series connection of the transistor pair means that each transistor must provide a wider current path therethrough than would otherwise be necessary, in order to sink sufficient current while the antifuse is blown. The wider current paths mean that the switching devices each occupy a large area on the associated chip in this era of ever-decreasing size for the functional devices of interest.
It therefore would be desirable to decrease the number of such relatively large programming and address elements, while preserving the informational value of the programmable elements.